Hi,
I am an entry level in custom PCB design. I want to use the BME280 IC with I2C in my picoballoon project. So I downloaded the Sparkfun BME280 breakout board eagle file and removed the unnecessary SPI components. Could someone check it and tell me if I haven't removed some crucial component? Also, I want to run this with a 3.3V level logic board (Adafruit Feather). Thanks.
Check what ?
And if weight is so important that you are using the bare BME280 sensor with a custom PCB for your Picoballoon project, I would dump the Adafruit Feather, a Pro Mini + SX1276/8 will be a lot lighter.
IIRC that sensor only needs a bypass capacitor on the Vcc pin. Pretty straightforward, I did it successfully with its sibling the BMP180 on one of my very first PCB projects. Worked like a charm. Do read the data sheet carefully, it has all the info you need on design of landing pads, required external components and placement of those components.